Too much of anything, even a helpful or healthy thing, can hurt you. Medication? Definitely. Water? Absolutely. Exercise? You bet. Vitamins? Quite possibly. 

Scientifically speaking, a vitamin is any one of a number of chemical compounds that help organisms stay healthy and grow. They may appear naturally in our bodies or in our food, or we may get them in the form of a pill, chewable cartoon-character-shaped tablet, or gummy.

We all need vitamins to survive—but that doesn’t mean we need to take vitamins. In fact, just about everyone (with a few exceptions, including pregnant women and people with absorption issues) can get all the vitamins they need by eating a balanced diet. Fruits and vegetables are naturally rich in vitamins, as are nuts, dairy products, eggs, and meat. On top of that, many of the foods on our supermarket shelves have been fortified with additional vitamins. 

Vitamin deficiencies do occur, and they can cause health problems. But these deficiencies are far less common than vitamin peddlers would have us believe. Today, more than half of Americans take at least one vitamin or supplement, and most of us don’t actually need them. 

If you’re eating a varied and healthy diet and consuming fortified foods and taking a vitamin, you could be overdoing it. This might seem like a good thing—if having enough vitamin D is good, having more must be better, right?—but it really isn’t. Your body requires a set quantity of each vitamin. Exceeding that quantity won’t make you healthier, but it could make you sick

Over-consuming vitamin C could lead to nausea, diarrhea, and stomach cramps. Too much vitamin D can cause vomiting, a loss of appetite, and kidney problems. An excess of B vitamins may cause nerve damage. You get the idea.

Still, to reach dangerous levels of any vitamin, you’d need to be hitting it pretty hard. A lethal overdose of vitamins is highly unlikely, but it is technically possible, the same way a lethal overdose of orange juice is possible. 

Still not sure if you’re getting enough? Check out the U.S. Food and Drug Administration’s table of Reference Daily Intake (formerly Recommended Daily Allowance, or RDA) recommendations. Like most FDA guidelines, the RDIs are based on a 2000-calorie diet, so you may need a little more or a little less. If you’re really concerned, talk to your doctor or a registered dietitian for more personalized recommendations.